One-dimensional nanostructures, such as nanotubes and nanowires, of different types of materials, such as elemental semiconductors, compound semiconductors, and oxides, are increasingly being investigated for a wide variety of future nanotechnology applications. As nanowires will be a critical interconnect element of any nanosystem, the ability to produce them at a desired location, in a controlled manner, is of great importance.
Of the numerous one-dimensional structures, silica nanowires are a subject of intense research in view of their potential for unique applications, such as localization of light, low dimensional waveguides for functional microphotonics, scanning near field optical microscopy (SNFOM), optical interconnects on a futuristic integrated optical microchip, sacrificial templates, biosensors, and optical transmission antennae.
Of the several methods used to produce nanowires, the Vapor-Liquid-Solid (VLS) mechanism for silicon whisker growth has proved to be very reliable for developing silica nanowires. In this method, the cluster acting as a seed for subsequent nanowire growth is either commonly synthesized by heating thin films or preformed. Recently, a method of using palladium ion implantation for the formation of catalyzing seed nanoclusters at or below the surface of a substrate and growing silica nanowires has been discovered. The vapor-liquid-solid model of nanowire formation facilitates controlled, localized, and directed bottom-up growth of silica nanowires. A series of diagrams explaining the ion implantation based seeding is shown in FIGS. 1A-E. As shown in FIG. 1A palladium (Pd) ions 10 are implanted on silicone (Si) wafer 11 through a mask. Then, as shown in FIG. 1B, PdSi clusters 12 form. FIGS. 1C-E show the growth of silica nanowires 13 using VLS.
Another method of growing nanowires is through the use of Chemical Vapor Deposition (CVD). CVD is a chemical process often used in the semiconductor industry to produce thin films. A substrate is exposed to one or more catalysts, which then react and/or decompose on the substrate surface to produce the desired deposit. In nanowires growth, CVD is a bottom-up approach. Catalysts, such as gold, are deposited on a substrate and act as an attraction site for nanowire formation. The substrate is put in a gas chamber containing the appropriate element, such as silicon. Atoms from the gas and catalysts attach, creating a chain or wire.
Although a method for growing nanowires in clusters exist, no method exists for controlled growth of nanowires in specific patterns/lines. An improved method is needed in the art for synthesis of nanostructures in a controlled pattern. Further, an apparatus capable of improved simultaneous optical and electrochemical sensing is needed.